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Pressure driven spin transition in siderite and magnesiosiderite single crystals
Christopher Weis1, Christian Sternemann2, Valerio Cerantola3
1Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, 44227, Germany. christopher.weis@tu-dortmund.de.
Scientific Reports
|November 30, 2017
Summary
Iron-bearing carbonates undergo pressure-induced spin transitions relevant to Earth's carbon cycle. We observed sharp transitions in siderite and magnesiosiderite single crystals up to 57 GPa, revealing insights into deep Earth carbon storage.
Area of Science:
- Geochemistry and Mineral Physics
- High-pressure experimental studies
- Earth's deep carbon cycle
Background:
- Iron-bearing carbonates are crucial for understanding the Earth's carbon cycle and potential deep Earth carbon storage.
- Investigating their properties at high pressures is essential for modeling deep Earth conditions.
Purpose of the Study:
- To elucidate the pressure-driven magnetic high spin to low spin transition of siderite (FeCO3) and magnesiosiderite ((Mg0.74Fe0.26)CO3) single crystals.
- To probe the iron 3d electron configuration under extreme pressures up to 57 GPa.
Main Methods:
- Utilized diamond anvil cells to achieve high-pressure conditions.
- Employed X-ray Raman scattering spectroscopy to directly probe the iron 3d electron configuration.
- Investigated single crystals of synthetic siderite and magnesiosiderite.
Main Results:
- Observed an extremely sharp spin transition in siderite at 40.4 ± 0.1 GPa with a soft helium pressure medium.
- A broader transition (4.4 GPa) and shifted pressure (44.3 ± 0.4 GPa) were noted for siderite using argon, attributed to pressure gradients.
- Magnesiosiderite showed a similar transition pressure (44.8 ± 0.8 GPa) when loaded with argon, indicating no compositional effect on transition pressure.
Conclusions:
- The pressure-induced spin transition in iron-bearing carbonates is sensitive to pressure gradients within the sample medium.
- No compositional effect on the spin transition pressure was observed in the studied magnesiosiderite.
- Spectra within the spin crossover regime suggest coexistence of high- and low-spin configurations within single crystals.
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